It is often necessary to cool hot solids from various industrial sources, and generally it is also desirable to recover the heat from the solids. The decline of world petroleum crude reserves has led to the consideration of various alternate hydrocarbon sources, e.g., shale oil. Shale oil, one of the world's most important synthetic hydrocarbon sources, is now being developed as an alternate source of refining feedstocks. The shale rock is crushed and retorted at high temperatures to recover the oil from the rock. In an industrial process, after removal of oil from the shale rock, great amounts of hot, sometimes sticky shale particles must be cooled, and the heat recovered therefrom to provide an economic operation.
There are a number of problems associated with cooling large masses of particulate solids. Though the preponderance of the particulate matter are quite small, the particles are nonetheless generally of fairly wide range of size distribution, and at elevated temperatures the solids particles are sometimes sticky, which can restrict movement of the particles, and produce agglomerates. Conventional solids cooling is generally carried out in one of two major ways: first, by the use of fluidized beds; and, secondly, by the use of rotary coolers. In the use of fluidized beds to cool the solids, and recover the process heat, a large amount of the heat is given up to the fluidizing medium. The remainder (40-60%) can be absorbed by heat exchange within the bed. More heat is transferred to the stack via the fluidizing medium, and less heat to the process coil. Entrainment of solids is high, this resulting in the need for large clean up devices; and potentially, the need for additional heat exchange equipment. The ability of conventional fluidized systems to handle wide particle size distributions leaves much to be desired.
Rotary coolers too are of limited value for use in the recovery of heat from solids. They are large in size and contain many moving parts. One particular problem is with the rotary cooler joints in that they cannot adequately handle the two phase, high pressure, fluids. In particular, their limitation results in their not being able to generate high pressure steam which is often desirable in plant operation.
It is, accordingly, the primary object of this invention to obviate these and other of the disadvantages of conventional fluidized bed coolers and rotary coolers.
A particular object is to provide an apparatus, or unit containing a solids medium-coil cooling system wherein solids are cooled and much more heat is transferred to the process coil than to the fluidizing medium.
A further and more particular object is to provide a solids medium-coil cooling system as characterized wherein solids of fairly wide particle size distributions are cooled.
These objects and others are achieved in accordance with the present invention, characterized generally as a solids cooler comprised of a housing having enclosing walls, inclusive of side walls, end walls, and a perforated plate, or distributor which separates the housing into two compartments, a first upper compartment, and a lower compartment, or plenum, further subdivided into several chambers, an elongate tube type heat exchanger located within the upper compartment through the inside of which a coolant can be passed, a hot particulate solids inlet for the delivery of hot particulate solids into the upper compartment to form above the preforated plate, or distributor, a bed of particulate solids which can be expanded to cover said tube type heat exchanger by the injection of an inert or non-reactive gas into the plenum chamber, the gas entering the bed through the perforations within the plate, or distributor, and a cool particulate solids outlet through which the cooled particulate solids are discharged after heat exchange through the walls of the heat exchanger tube bundle with the coolant fluid.
The hot particulate solids are introduced into the upper compartment through the solids inlet, preferably at the surface level of the expanded bed. The perforated plate, or distributor, is sloped downwardly between the solids inlet and solids outlet at an angle ranging from 1.degree. to about 10.degree., preferably from about 2.degree. to about 8.degree., measured from horizontal, for gravity to aid the flow of solids, particularly the large solids particles which slip and slide along the upper surface of the distributor plate, moving from solids inlet to solids outlet. The perforations within the distributor, are jets sloped directionally such that the inert gas introduced from the plenum chamber through the perforated distributor plate is directed toward the cooled solids outlet, an angle ranging from about 0.degree. to about 45.degree. preferably from about 0.degree. to about 25.degree., measured from vertical. The larger solids, as suggested, slip and slide along the upper surface of the perforated plate, or distributor, from the direction of the solids inlet to the solids outlet, aided by the inclination of the perforated plate, or distributor, and angularly directed jet openings, and the smaller particles are stratified as a layer, or as layers, above the larger particles and move directionally in generally similar fashion.
These features and others will be better understood by reference to the following more detailed description of the invention, and to the drawing to which reference is made. Similar numbers are used in the drawing to designate similar parts, or components, in the several different views, and where there are a plurality of similar parts, subscripts are used with the numbers. Where a whole number is used to designate an apparatus part, or component, and then subscripts are introduced with the whole number to designate the component parts, the whole number is intended in the generic sense. Where subscripts are introduced to designate an apparatus part, or component, and then dropped, the number from which the subscript, or subscripts, are dropped are intended to apply in the generic sense.